1. The most basic trig properties on one sheet.
2. Some well-known proofs of Pythagorus's Theorem.
3. A proof by areas of the sin(A+B) formula.

These are copied from
https://www.math.wisc.edu/undergraduate/calculus-students-page
and
http://www.math.wisc.edu/~miller/old/m222-10

An on-line text book that I like is
Elementary Calculus: An Infinitesimal Approach by J.Keisler
See Chapter 7 on Trigonometry.